Boat propulsion system



Oct. 1, 1963 P. R. BALDWIN 3,

BOAT PROPULSION SYSTEM Filed Dec. 11,1959 3 Sheets-Sheet 1 INVENTOR. PAUL R BALDWIN BY 19. M71444 HIS ATTORNEY Oct. 1, 1963 P. R. BALDWIN 3,105,455

BOAT PROPULSION SYSTEM Filed Dec. 11, 1959 '3 Sheets-Sheet 2 IN VENTOR. PA (/4 E. EAL D WIN BY ,0; flea HAS A TTORNEY Oct. 1, 1963 P. R. BALDWIN BOAT PROPULSION SYSTEM 3 Sheets-Sheet 5 Filed Dec. 11, 1959 PAUL E. BALDW/.N

HIS A TTOENEY a a rs r r f i 3 W5 4E5 s m an ea -1 f maa i 53 digitalis i? gr Fed rat d ea 1 1963 traveling at very low speeds the tilt is slightly downward 1 in a forward direction. This provides a decided advan- BQA'E SYSTEM Paul R. Baldwin, State Rte. 252, V alley (Iity, ()liio Filed Dec. 1?, 19:79, Ser. No. $55 ,935 2 Claims. or. 115-67) This invention relates to boats and more particularly to an improved boat propulsion system.

In the past it has become common practice to propel boats by the use of screw propellers. These propellers are located at the stern of the boat, usually opposite to a keel or a false keel and between the keel and a rudder. Since the propellers, there may be one or more, are usually located below the hull, the drive shaft usually passes through the bottom of the hull at an angle and the propellers are on the end of the drive shafts. Thus, the propellers are actualy tilted at an angle, especially in the smaller craft, and the thrust from the propellers is forward and upward. The propeller, therefore, wants to climb out of the water and is only prevented from doing so by the weight of the boat. These boats, being de* signed to cruise with their bows out of the water are not helped by thusly mounting the propeller which tends to force the stern up and the bow down. This is particular 1y noticeable when a boat is started or when suddenly accelerated as at the start of acceleration the bow dips and the stern comes up.

Still other disadvantages reside in the fact that the wake of the boat interferes with the propeller. This comes about in several ways, the more apparent being that the Wake forms a trough and the tips of the blades may break through the surface of the water or even suck air down into the propeller, which causes the propeller to revolve at a high rate of speed, losing its bite on the water and causing erratic operation of the engine due to inconstant load. Too high a speed for a propeller mounted at this angle causes cavitation and resultant wear.

Furthermore the wake is following the boat and the propeller may be operating in a zone of water which fol lows the boat and the lades when at the low point are in still water, since the greater thrust is from the blade at the lowest point, this provides undue strain on the pro peller blades as well as the shaft bearings, reducing their life.

By the present invention I am able to substantially eliminate all the above-named deficiencies and to provide further advantages which are not present in conventional propeller drives.

Briefly, my invention contemplates placing the propellers amidship or slightly aft or forward of the center of gravity, which is usually amidship, and so positioning the propeller that the thrust provided thereby is in a horizontal direction so that all of the forces of the propulsion system are in a horizontal forward direction.

Preferably the propeller and its driving shaft are supported by a nacelle which is secured to the underside of the hull.

Placing the propeller under the hull and slightly and to one side or the other of amidship or amidship provides several advantages. it prevents air from being sucked into the propeller and decreasing its efificiency. It keeps the propeller completely submerged at substantially all times and eliminates the need for reducing engine r.p.m. due to the propeller coming out of the water, which is common in nearly all boats, particularly in water that is rough or has rolling seas. It also operates in a zone or region of the water where there is no wake.

The tilt of the propeller and the nacelle is such that at cruising speed the propeller axis and the nacelle are substantially horizontd. When the ship is at rest or tags in that at low speeds vector forces due to the pull of the propeller are such, the propeller being disposed close to the center of gravity, that the tendency is to pull the stern down and the bow up and the horizontal stability is improved and pitching reduced. Thus even at low speeds the elliciency of the boat increases because the bow comes up and the boat is not as deeply submerged, as is usually the case, just behind the bow. As the speed is increased and the bow comes up still further the propeller and its nacelie come up to a horizontal position. At this time the efficiency is even greater, because the pull is all in a straight forward direction and parallel to the surface of the water. In other words, the push or pull of the propeller is in a straight forward and horizontal direction. There is no upward thrust movement which merely raises the boat out of the water and does not materially add to the forward speed as in conventional systems. As is well known to those versed in the art, in stem drive vessels, it is nearly impossible, without the use of complicated universal joints, to drive the propeller so that the thrust is horizontal, but it is usually in an upward direction and this condition is unduly exaggerated as the bow comes up ad the stern goes down, with the result that the low riding stern causes a very severe wake and/or rooster tails and sometimes a trough so deep that it exposes the tips of the propeller blade, making it necessary to mount the propeller lower, increasing the angle and causing the upward thrust to be even greater.

Due to the movement of the water under the hull by the propeller of the present invention, the skin resistance effect of the water on the hull is decreased. Since all of these factors tend to increase the propeller efficiency the actual rpm. may be reduced, which causes less wear on all parts including the engine. 'P'ropeller life is also increased because with the lower propeller rpm. there is less cavitation. reduction in also reduces the slip ratio which provides for increased eiiiciency, especially at higher speeds,

Still other advantages of the invention, and the invention itself, will become more apparent from the following description of some embodiments thereof, which are illustrated in the accompanying drawings and form a part of the application.

In the drawings:

PEG. 1 is a side elevational view of a motor boat in a stationary position, showing my invention;

FIG. 2 is a side elevational view of the boat of FIG. 1 in the position it attains at cruising speeds;

FIG. 3 is a fragmentary view on an enlarged scalof the power drive of my invention;

FIG. 4 is a similar view of a modification thereof;

FIG. 5 is a fragmentary elevational view of the boat of FIG. 1 from the bow;

FIG. 6 is a side elevational view of a boat in a cruising position and illustrating a modified form of drive;

FIG. 7 is a fragmentary elevational view of the boat of FIG. 6, taken from the stern;

FIG. 8 is a vertical section through a nacelle and strut of a drive similar to FIG. 3 with the interior parts shown in elevation;

FIG. 9 is a section on the line 9-9 of FIG. 8;

FIG. ll) is a fragmentary rear elevational view of the drive similar to that of lFlG. 9;

PEG; 11 is an enlarged fragmentary section thereof;

FIG. 12 is a fragmentary view taken from the bow of another modification of the invention;

FIG. i3 is a fragmentary side elevational view of the embodiment of FIG. 12;

PEG. 14 is a fragmentary elevational view of the stern of a boat, taken from the side, of tion of the invention;

FIG. 15 is a side view of a hydroplane embodying the invention;

FIG. 16 is a front elevational View thereof;

FIG. 17 is a fragmentary view of the bottom of a boat and a nacelle, shown in section, and illustrating another embodiment of the invention; and

FIG. 18 is a section on the line ll$ ofFIG. 17.

Referring now to the drawings throughout whic. like parts have been designated by like reference characters, as best shown in FIGS. 1 and 2, a boat hull is provided, having a bow l2 and a stern 14. The bottom or keel decreases in depth from the bow to the stern and is provided with a false keel 16 which serves as a protection for the hull proper and also prevents drift of the boat when blown by the wind. To the rear of the false keel, there is provided a rudder 17 supported on a lower bearing 18 extending rearwardly from the false keel. The upper end is connected to a rudder post 19 which extends into the hull and is connected to a suitable tiller or wheel for steering purposes, not shown. Usually there is a space between the forward edge of the rudder and the false keel in which a screw propeller is disposed. Frequently, however, dual propellers are used in which event they are disposed at opposite sides of the rudder, usually at the same longitudinal position as a single propeller. At a state of rest, the hull usually takes a position in the water as indicated by the line 13.

When the boat is under way, FIG. 2, the bow of the boat rises until the true keel is substantially parallel with the surface of the water. At this time the false keel extends at an angle to the water surface and prevents sidewise drift of the boat through the water in event there is a wind from either side of the boat.

As is well known to those versed in the art, usually another modificathe propeller shaft or shafts extends through a seal in the bottom of the boat at an angle. This angle is usually such that the propeller as a whole is inclined, the top being farther toward the stern than the bottom. Under such conditions the thrust by the propeller is slightly upward as well as forward, and when the bow rises this condition is aggravated so that at high speeds the thrust is still more in an upward direction with a result that there is a tendency to raise the stern and lower the bow. This is supposed to be overcome by the passage of the water under the boat, but as a matter of fact the boat merely rises and rides on its stern causing a much more severe wake and high angle of attack for the bottom of the boat. This causes the keel to rise out of the water, increasing drift and visibility is reduced due to the high rise of the bow. The angle is also reflected in the position of the deck which is no longer level and is uncomfortable for the boats occupants. This results in a division of the power thrust, more of it being in an upward direction as the speed increases and less of it being in a forward direction.

Ideally therefore, the objective is to utilize all of the power to move the hull forward and the only forces which raise the how are the [forces acting on the bottom of the hull by the water which becomes the least when the bottom of the hull comes to a position parallel with the water surface. This condition can never be perfectly realized when the propeller is disposed at the conventional angle, which angle increases with speed.

As shown in FIG. 1, I provide a nacelle 29 which is connected to the bottom of the boat. The nacelle may be streamlined to provide a minimum of resistance to water flow and to enhance the directive effect of the propeller. If a single propeller is to be used, the false keel may be cut away and the nacelle disposed in the gap so provided. The nacelle supports a propeller shaft 24, FIG. 3, which is journalled in water lubricated bearings 25 and 25', fore and aft. The shaft projects through the forward end of the nacelle and carries a screw propeher 2 6.

It will be noted that the center line through the propelle shaft and propeller hub is such that when the hull is in a cruising position, FIG. 2, it is parallel to the surface of the water. At a state of rest, FIG. 1, this center line inclines downward.

The propeller shaft is driven from the engine by a shaft 30 which extends through a rotary water seal and bearing 31 and has a pinion gear 32 in mesh with a second pinion gear 33 carried by the propeller shaft. Obviously other types of gears than those defined may be used.

Water may enter through the front bearing 25 and escape through a port 27 at the rear of the nacelle as well as a port 27' at the lowest portion of the nacelle. The port 27 may be open or closed as desired.

The invention adapts itself most readily to the use of dual propellers which may be driven from single or dual engines.

In this instance, separate nacelles of each propeller are provided connected to the hull on opposite sides of the keel. This is shown best in FIGS. 1, 2 and 5.

It should be pointed out that the nacelle is preferably slightly larger in diameter than the propeller blades and thus acts as a skeg protecting the propeller.

ireferably the nacelle should be sufiiciently sturdy and so disposed on opposite sides of the keel that they, together with the keel provide a support for the hull when the boat is removed from the water, eliminating the need for a cradle or the laborious use of blocks to properly hold the boat when it is in storage or being conditioned for service.

As can best be seen from FIGS. 2 and 3, the nacelle may be a partial nacelle, the upper part being attached to the boat throughout almost or all of its length. This is particularly desirable in connection with shallow draft boats. When it is used in conjunction with boats having a deeper keel, the nacelle may become a substantially complete nacelle 20 connected to the hull by a relatively narrow streamlined hollow stem 35, as shown in FIGS. 6 and 7. Preferably the nacelle should be located at or near the center of gravity for the hull.

It will be appreciated that power may be delivered from the engine or engines to the propeller shafts 24 in many different ways. In KG. 4 I have shown a belt drive. In this instance the transmission would be provided with a power take-oil shaft which would have a sheave or a multiple sheave over which a plurality of V belts 36 would be trained, the belts passing down through an opening 37 in the bottom of the hull and being trained around a multiple type pulley 33 secured to the shaft 24. In this event, the bottom drain hole 27 would be closed by a suitable plug and excess water in the nacelle would be pumped out by a pump driven by the engine and connecting through a conduit 39 to the bottom of the nacelle. The belt 36 may be a series of belts or it may be one of the well known belts having a plurality of wedge shaped pulley engaging portions connected together by a single backing.

As a modification of the invention illustrated in FIGS. 8 and 9, I contemplate that the nacelle be mounted on a connector or strut 4% so that the degree of tilt may be controlled or varied. In this instance, the connector or strut 49 is provided at its lower end with outwardly extending arcuately curved flanges 41. The nacelle is provided with cooperating arcuately curved ways 42 which are inwardly turned and interlock with and hold the flange 41. The nacelle may be slid backward and forward on the ways and when so slid due to the arcuate contour of the ways, the tilt of the nacelle is changed,

In this case, the drive shaft 30 is provided with means to permit inclination thereof as the pinion gear is moved forward or backward, such as a universal joint 43.

The device of FIGS. 8 and 9 lends itself as an assemly which may be attached to boats having different hull designs, where the crusing angle may vary through a wide range. Once the propeller cruising angle is determined, the nacelle may be adjusted to the position where it operates most efficiently and then secured in that position. It may be desirable, however, to provide a nacelle which may be tilted at various angles, which may be changed with the speed of the boat. In this event, a slight modification of the structure shown in FIGS. 8 and 9 can be made, as illustrated in FIGS. 10 and 11. In this instance, the flange 42 on the nacelle has a gear rack 43 secured thereto and an adjusting spur gear 44 is in mesh with the teeth of the rack. A shaft 45, connected to the gear 44, extends up through the strut and the bottom of the hull, where it is supported by a bracket 46 and is provided with an adjusting handle 47. When the handle is rotated the gear 44 is rotated and the rack and its nacelle is moved forward and backward. The sliding surfaces between the nacelle and strut being arcuate, the angle of tilt of the nacelle and its propeller may be adjusted to the desired degree. The handle 47 may be calibrated or other suitable indicator connected to the control shaft in order that the position of the nacelle will be known at all times.

Although I have shown the use of shafts and gears and belts for connecting the propeller to the engine, it will be apparent that the construction lends itself equally well to the use of fluid drive couplings.

Although I have described the combination of the nacelle and propeller being such as to have the nacelle act as a skeg or protector for the propeller and also providing a support for the boat when it is out of the water, 1 also contemplate that the bare essentials for supporting a propeller and its drive amidship may be used. This would be particularly desirable in connection with boats which are designed to cruise at high speeds. For instance, as illustrated in FIGS. 12 and 13 the strut 50 is considerably smaller, being large enough to house the power shaft and still provide a support for a gearing in in a small housing 51 from which a propeller 52 is driven. The entire assembly could be substantially as provided for a conventional outboard motor except that the propeller should be a tractor operating type rather than the pusher type. It likewise would be designed so that the thrust is in forward horizontal direction at cruising speeds.

It is also contemplated that the invention may be used with existing boats having conventional power plants. In FIG. 14 there is illustrated the stern portion of the hull of a conventional boat wherein the propeller shaft 61 comes through the boat at the usual angle and is supported near its end by the usual bracket 62. In this instance, the propeller is removed and a bracket adapter, which comprises a housing 64 having mounted therein gears 65 and 66 is secured to the bracket by a clamp 67. The gear 65 replaces the propeller that is removed and the gear 66 in mesh with the gear 65 has a shaft 68 connected thereto. The shaft 63 extends forward and amidship of the boat and is supported by a strut 69 connected to the bottom of the boat. The propeller 79 is mounted on the shaft 63 forward of the strut. The shaft 68 is thus supported at each end, at the rear by the housing and at the front by the strut.

The above can be installed in a minimum of time on existing boats with little or no modification thereof other than removing the propeller and securing the forward strut to the bottom of the hull. The forward strut can be made of two parts which are adjusted one within the other to vary the tilt angle if desired. Obviously should a universal drive be made it would be desirable to provide a universal joint, or other flexible coupling in the shaft 68, preferably at the rear housing to enable the shaft to be moved vertically at the front end. It is apparent that the structure of FIG. 14 can be used with 55 boats having a single power plant and propeller as well as boats having more than one power plant and propeller.

It will also be apparent that my invention lends itself readily to boats using the hydrofoil principle as shown in FIGS. 15 and 16. :In this instance, the nacelles 78 could be mounted on opposite sides of the hydrofoil planes 71 and the power delivered to the propeller 72 through the hydrofoil struts 7 3.

It should also be pointed out that jet propulsion members may be used to replace the propellers.

In FIGS. 17 and 18 I have illustrated my invention as applied to the hull of a boat wherein the tilt of the propeller may be adjusted within the nacelle and from within the boat. T 0 this end the engine shown at 89 is provided with the usual transmission including a reversing gear 81. A power shaft 82 extends from the transmission and is supported at its end in a bearing 33. A multiple groove sheave 84 is secured to the shaft and carries a belt or belts 85 which extend down through a port '85 in the bottom of the hull.

A nacelle similar to that shown in FIG. 4 is secured to the bottom of the hull.

Also secured to the hull is a downwardly extending strut 37 which is flanked by a pair of plates 83 that are pivotally connected to the strut 87 and 89. The plates 88 are connected to and support a bearing 91 which in turn supports the front end of the propeller shaft $2, the shaft extending out of the nacelle and having a propeller 93 thereon. The rear end of the shaft 92 is journalled in a bearing member 95, which consists of a pair of side plates 915 connected together at their front edges by a web 9'7. A strut 93 secured to the bottom of the hull extends down between the plates 96. The web 97 carries a hook bolt the hook end 99 of which extends through an arcuate slot in the plate 98. Thus the entire propeller shaft assembly may be tilted about the pivot 89 and held in the desired adjusted position by the bolt 99. Obviously means such as idlers will be used to take up the slack in the belt or after the desired adjustment is made the correct size belts would be used. Also the shaft 82 may have a flexible connection to the transmission and the support for the bearing 83 being movable so that proper parallelism may be maintained between the sheaves.

The device has the advantage that it provides a tilt adjustment for the propeller which may be adjusted through port %6. Furthermore the angle of the propeller may be adjusting without changing the position of the nacelle.

In addition to the other advantages heretofore enumerated the arrangement of dual propellers under or near the center of the boat allows one propeller to be run forward and the other backward enabling the boat to turn within its own length on its center axis, which is not possible in other dual propeller devices.

It will be apparent that the shape of the nacelle may be varied. Preferably it is desirable to have it slightly larger than the propeller for the protection it affords. It should be noted, however, that it may be greatly reduced in size, being only large enough to provide a support for the propeller shaft. This would eliminate all unnecessary drag and thus enable greater speed to be attained.

Having thus described my invention, in an embodiment thereof I am aware that numerous and extensive departures may be made therefrom without departing from the spirit of the invention as defined in the appended claims.

1 claim:

1. A propulsion system for a boat having a hull and a keel running from the bow to the stern comprising motor means disposed within the [hull near the stern, a pair of bladed tractor propellers each of which is supported under the hull on opposite sides of the keel ahead of the stern and aft of the center of gravity, said pro 7 5,3 pellers being wholly disposed under the hull and above References Cited in the file of this patent the bottom line of the keel, a pair of propeller shafts con- UNITED STATES PATENTS nected to said motor means and extending from the rear of the hull forward, said propellers being carried on the 2 2;; gz g forward end of said shafts and arranged to be operated 5 1 227784 H 1914 in opposite directions, the axes of said propellers being 1605376 l 32 1926 parallel to the center line of the keel and inclined down- 2196706 lqaoinskars A r 1940 Ward and forward when the boat is at rest and arranged 2381622 shgppard g 1 19115 to be parallel to the surface of the Water When the boat 2460339 j g 4 is travelling at Cruising SPeed- 2i9l8j029 Legat l)ec. 22, 1959 2. A system as described in claim 1, wherein the propellers are disposed in close proximity to the hull where- FOREIGN PATENTS by the force of the Water moved by the propellers is 41,863 Denmark Mar. 7, 1930 against the hull and alongside the keel. 597,570 Great Britain J an. 29, 1948 

1. A PROPULSION SYSTEM FOR A BOAT HAVING A HULL AND A KEEL RUNNING FROM THE BOW TO THE STERN COMPRISING MOTOR MEANS DISPOSED WITHIN THE HULL NEAR THE STERN, A PAIR OF BLADED TRACTOR PROPELLERS EACH OF WHICH IS SUPPORTED UNDER THE HULL ON OPPOSITE SIDES OF THE KEEL AHEAD OF THE STERN AND AFT OF THE CENTER OF GRAVITY, SAID PROPELLERS BEING WHOLLY DISPOSED UNDER THE HULL AND ABOVE THE BOTTEOM LINE OF THE KEEL, A PAIR OF PROPELLER SHAFTS CONNECTED TO SAID MOTOR MEANS AND EXTENDING FROM THE REAR OF THE HULL FORWARD, SAID PROPELLERS BEING CARRIED ON THE FORWARD END OF SAID SHAFTS AND ARRANGED TO BE OPERATED 